This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 23 |
| 5 | 181 |
| 6 | 1812 |
| 7 | 22037 |
| 8 | 315569 |
| 9 | 5201602 |
| 10 | 97009833 |
| 11 | 2019669961 |
| 12 | 46432870222 |
| 13 | 1168383075471 |
| 14 | 31939474693297 |
| 15 | 942565598033196 |
| 16 | 29866348653695203 |
| 17 | 1011335905644178273 |
| 18 | 36446897413531401020 |
| 19 | 1392821757824071815641 |
| 20 | 56259101478392975833333 |